HU193927B - Polishing compositions of corundum content - Google Patents

Abstract

The cpd. contains 40-70% electrically prepd. diamond spar of 41-355 microns in particle size, 3-6.5% sodium polyacrylate additive to increase viscosity, itself having viscosity of 0.4-5 Pa.sec. and solids content of 10-15%, 0.8-1.5% fatty alcohol sulphonate with C10-C18, 0.8-1.5%, pref. 1% aliphatic alcohol mixt. with C6-C10, surface stabiliser additive, also in some cases, 1.5-6% pref. 3% corrosion inhibitor, such as 10% alkyl pyridinium halogen soln. in alcohol and sufficient distilled or deionised water to produce an overall viscosity of 0.3-1.5 Pa.sec. - The sodium polyacrylate additive is mixed with 80% of the distilled or de-ionised water in a high-shear mixer for 5-20, pref. 10 mins. 0.8-1.5% fatty alcohol sulphonate is added and mixed in for 1-2 mins. 0.8-1.5% pref. 1% aliphatic alcohol is added and mixed-in for 2-5 mins. 40-70% diamond spar particles are added and mixed in for 5-10 mins. The remaining 20% water is added and mixed in for 2-3 mins. In some cases 1.5-6%, pref. 3% of a corrosion inhibitor e.g. a 10% alkyl-piridinium halogen soln. in alcohol, is added and mixed in for 5-7%.

Description

BACKGROUND OF THE INVENTION The present invention relates to an easy to regenerate corundum abrasive composition for use in grinding hard magnets (e.g., ticonal, 'alnico, rare metal cobalt, and carbide inserts).

For grinding carbide inserts and magnets, silicon, titanium, boron carbides are usually used as abrasives, either individually or in combination, and ground to a suitable degree of fineness. In addition to carbides, alumina is also recommended for the machining of carbides (U.S. Patent No. 47,976). However, this is not suitable for grinding but for polishing as the alumina is not hard enough.

Other carbide oxide mixtures are used, other than for grinding carbides, but mainly for polishing. According to GD 33,778, _{3 to} 4% by weight of fluoride is added to a mixture of CaCO ₃ and MgCO ₃ to form relatively hard, glassy oxide particles for polishing. German Patent No. 2,001,612 proposes a mixture of limestone and corundum particles for polishing. GD 90830 also proposes a mixture of tin (II) oxide, Al ₂ O ₃ , iron oxide, chromium (III) oxide, titanium (IV) oxide, also for polishing medium hardness materials. According to GD 64664, cerium (IV) oxide is added to iron (III) and iron (II) oxides to increase hardness, also in polishing paste. NDK 50 717 discloses the use of (medium hard) aluminum silicates for grinding. According to GDR Patent No. 47,985, quartz sand is used as an abrasive material which is also suitable for machining medium hard materials. Hungarian Patent Nos. 147,261 and 170,264 disclose the preparation and use of polished earths. These materials are very expensive and have the disadvantage that their waste is harmful to the environment and therefore it is very costly to recycle the components that are still usable from the waste of the used abrasive composition. However, grinding also requires a carrier solution of a viscosity which has a viscosity sufficient to prevent the release of the abrasive particles and therefore enhances the grinding effect. However, the solution should well moisten the surface of both the abrasive material and the abrasive grains to ensure that the abrasive fines do not adhere to the work surface or reduce the abrasive effect of the suspension. In the composition returned to the collection tank, the solids, since they have the same sign of the electrokinetic potential, do not coagulate. The same surface charge or electrokinetic po2 potential ensures that finished workpieces can be washed with clean water.

At the interface of solid particles, the solvent and solutes (ions) form a molecular bilayer, one of which stably binds to the surface of the solid and the other forms a diffuse boundary. When flowing, the two layers move relative to one another and there is a potential difference between them, called electrokinetic - or zeta - potential. The magnitude and sign of this voltage difference strongly depends on the concentration of dissolved ions or surfactants.

The solution must also ensure that neither the grinding equipment nor the workpieces are corroded.

Finally, it is easy to coagulate the components of the composition from the waste water containing the spent composition. The abrasive materials described in the foregoing patents do not wash off the workpiece surface with water and do not meet the requirements listed above. Currently, water soluble amino and phenoplastics with very low surface charge are used to increase viscosity. These resins are based on urea, formaldehyde and melamine. The disadvantage of these resins is that they are unstable in aqueous solution, they polymerize very rapidly under the influence of acid, alkali, chloride ion or heat, which can cause serious malfunctions.

The use of viscosity inducing alkyd resins is described in German Patent No. 2001612, which combines the resin with chloro-paraffin to form a highly acidic, corrosive and environmentally-contaminating mixture which, due to the water-insolubility of chloro-paraffins surface, which subsequently interferes with electroplating, for example.

Another large group of viscosity enhancing additives are amines which are commonly used in the preparation of various industrial emulsions. Of these, mention may be made of the mixture disclosed in GDR 99 599, which emulsifies from a mixture of diethanolamine, ethylenediamine, hexamethylenediamine. The disadvantages of amines are that they are very basic and can cause environmental contamination and, due to their high reactivity, can even produce toxic products in the environment. They also have the disadvantage that higher and higher amines are insoluble in water (e.g. hexamethylenediamine) and can cause harmful, irreversible film formation on the workpiece. It is also relatively expensive compared to other materials. The stability of amine-containing emulsions can be greatly influenced by the presence of foreign metal ions in the compositions, which is a disadvantage in their use. means. Other carrier media for oils, greases, and waxes for abrasive compositions, e.g. pastes. The main disadvantage of these is that, although they are often mixed with emulsifiers, they leave behind a film, which cannot be washed away with water, which cannot be removed to the extent that subsequent galvanization is not disturbed. A further disadvantage is that the waste oil is later disposed of as a polluting waste.

Some descriptions are petroleum jelly, spindle oil, stearic acid and palmitic acid in solutions of amyl alcohol and ethyl alcohol, Hungarian Patent No. 147,261, Sheep Fat and Paraffin, US Patent No. 1,250,579, Fat and Resin Mixture, Hungarian Patent Application No. 170,364, Paraffin. , a mixture of spindle oil and synthetic detergents as a carrier medium for abrasive pastes.

The compositions described in those patents have poor electrochemical properties and are therefore unstable. Currently, various plant extracts are blended into the compositions to form electrochemically favorable surface charges and to prevent corrosion.

These are highly complex, difficult to access and costly materials. For example, ipecacoanic acid, emetine (cephelin methyl ether) and other alkaloids, which are toxic or toxic, can be found.

The disadvantages of the known blends, apart from their high cost and their difficult availability, are that there is no known product to which various detergents should have been added to wash the finished pieces. On the other hand, they must also contain separate corrosion inhibitors. In the course of the examination of known products, it was also found that during surface grinding, the surface charge and the electro-kinetic potential changes several times and therefore very precise abrasion conditions are required to avoid malfunctions. It is an object of the present invention to provide an abrasive composition, in particular for hard magnets and carbides, which is more stable than the above-described compositions, is free of environmental contaminants and is readily precipitated and reused in waste water.

This can be achieved by increasing the viscosity by using a polymer having a high surface charge and a medium molecular weight polyScrylic acid sodium.

In order to stabilize the surface charge, C 10 -C 18 fatty alcohol sulfonates and

C 6 -C 10 aliphatic alcohols, preferably hexanol or isooctyl alcohol, are added to the composition.

The abrasive mass containing the above components provides all the materials used for grinding with the same sign and strong surface charge, including the electro-corundum used as the abrasive material, thus preventing its precipitation and adhesion to the surface.

The abrasive used is an electro-corundum having a particle size of 41 to 255 µm.

It is also desirable to include corrosion inhibitors, such as alkylpyridinium halides, in the abrasive composition when grinding parts that are prone to corrosion.

The present invention relates to an abrasive composition containing corundum, preferably for grinding hard magnets and carbides. The composition comprises a viscosity-increasing additive of 50-70% by weight of a polyacrylic acid sodium having a viscosity of from 100 to 500,000 molar weight, preferably having a viscosity of 1 to 2 Pa.s, a solids content of 10-15% by weight, 10 to 18% by weight. a carbon fatty alcohol sulfonate and 0.3-1.0% by weight of a C 6 -C 10 aliphatic alcohol (especially hexanol or isooctyl a-1 alcohol) with a surface charge stabilizer, optionally 2.5% to 3.5%, preferably 3% by weight , a corrosion inhibitor such as a 10 wt% alcohol solution of afkylpyridinium halide and distilled or deionized water.

Preferably, as the polyacrylic acid sodium, Solac T, a medium polymerization grade, is used which is an aqueous solution having a viscosity of 1 to 2 Pa.s and a solids content of 10%. The molecular weight of the composition is most suitable if it is in the range of 100 to 500,000, because a relatively low solids content can be used to form a solution of appropriate viscosity which does not coagulate the abrasive composition and does not abruptly reduce its viscosity during grinding. Changing the molecular weight between given limits is not a problem because the higher degree of polymerization or a product with a higher viscosity can be adjusted to the required viscosity by simple dilution.

The polymer is used in our grinding composition in a lower dry matter form. For dilution, distilled or deionized water is used. Dilution is carried out in a rapid shear mixer since the polymer is a gelatinous, very dense material. DEZ-C and ULTR A-TURR AX ^{R can be} used as such mixers.

By means of the above-mentioned mixers and the well-chosen mixing times for each component, it is possible to achieve good homogenisation and uniform absorption of the individual constituents on the surface of the abrasive grains.

To stabilize the surface charge of the particles, fatty alcohol sulfonates and aliphatic al3

A mixture of -3193927 alcohols, preferably hexanol or isooctyl alcohol.

Preferably, the fatty alcohol sulfonate is Evanate B-29, a sulfonate of a C 10 -C 18 fatty alcohol blend. It is also possible to use a lauryl sulfonate which is e.g. IPATEX or TEKAPON brand product.

The electro-corundum used as abrasive grain has a particle size of 41 to 255 µm. Preferably, the composition used for grinding hard magnets has a particle size electro-corundum having a particle size of 150-175 µm and a composition for grinding carbides preferably between 125 and 150 µm, and preferably a 41-59 µm sanding core.

The viscosity of the grinding composition is adjusted with distilled or deionized water.

Water cannot contain trivalent metal ions. The finished composition has a viscosity within the range of 0.3-1.5 Pa.s. Abrasive compositions having a viscosity of 0.3 to 1.0 Pa.s and preferably 0.3 to 0.5 Pa.s are preferred for hard magnets.

Preferably, the corrosion inhibitor is a 10% w / v solution of cetylpyridinium bromide in alcohol.

In the preparation of the abrasive composition according to the invention, the viscosity enhancing additive of polyacrylic acid sodium having a viscosity of 3-6.5% by weight, preferably 1 to 2 Pa.s, a solids content of 10-15% by weight and 80% by weight of distilled or deionized water is required. Stir in a high shear mixer for 5-20, preferably 10 minutes, add 0.8-1.5% by weight of C 10-18 fatty alcohol sulfonate. and the mixture is further stirred for 1-2 minutes, then 0.3 to 1.0% by weight of aliphatic alcohol having 6 to 10 carbon atoms is added and the mixture is stirred again for 2 to 5 minutes, then 40 to 71% by weight between 41 and 255 pm A particle size electro-corundum is added and the materials are stirred for a further 5 to 10 minutes, then the remaining 20% by weight of distilled or deionized water is added and stirring is continued for 2 to 3 minutes, optionally 2.5 to 3.5 by weight, a corrosion inhibitor such as a 10% alcoholic solution of alkylpyridinium halide is added and stirring is continued for 5-7 minutes. A stable abrasive composition having excellent properties is prepared. On the one hand, these favorable properties are due to the fact that the polyacrylic acid sodium used by us is a very stable polymer, the degree of polymerization does not change (no further polymerization or degradation occurs). On the other hand, the electrokinetic potential produced by the composition of the invention does not signify a change in concentration. After finishing the grinding, the spent composition is easily flocculated from the waste water with a small amount of 4, 10 to 10% by weight of citric acid and a solution of BaCl ₂ or NaCl.

Precipitation flakes also contain most of the organic matter, thus minimizing environmental contamination. It is also very easy to regenerate the material. By washing the slurry of the desired size with water, the slurry can be returned directly to the grinding compound, and the fine slurry passed through the screen can be recovered by magnetic filtration separators, which, once dried, can be recycled to powder metallurgy. The remainder consists only of particles that are too fine for the present process, but which can be used elsewhere as a polishing agent.

The abrasive composition of the present invention and methods for its preparation are illustrated by the following examples.

EXAMPLE 1 Polyacrylic acid sodium (viscous solids content 10% by weight), having a viscosity of 1.5 Pa.s (100-500,000 molar), was weighed into a ULTRA-TURRAX quick mixer. Distilled water is added to it, approx. 400 ml, and the mixture was stirred 10 times. Add 15 g of Evanate B 29 (C 10 -C 18 fatty alcohol blend sulfonate). After stirring for 2 minutes, 10 g of hexanol was added and stirring continued for 3 minutes. 900 g of EKF 100, 150-175 µm, were added and the materials were further stirred for 8 minutes.

Distilled water was added to the blender (about 100 mL) to adjust the viscosity to 0.9 Pa.s and stirring was continued for 3 minutes. The abrasive mass thus produced (about 1000 ml) is used for surface treatment of TICONAL hard magnets.

During grinding, the pressure on the workpiece is 0.3 MPa and 0.3 mm ³ for sanding. A mixture of 10 wt% citric acid and 10 wt% BaCl ₂ solution was mixed into the abrasive compound used. The precipitate was transferred to a sieve and washed with distilled water. The precipitate remaining on the sieve is reused for the production of abrasive pulp. The magnetic suspension is then recovered from the filtrate slurry with a magnetic filter separator. It is dried and used in powder metallurgy.

EXAMPLE 2 Polyacrylic acid sodium (brand name: Sokarol T, solids content: 10% by weight), having a viscosity of 1.5 Pa.s (100-500,000 molar), was weighed into a ULTRA-TURRAX rapid shear mixer. Distilled water (450 mL) was added to the mixture

Stir for -4193927 minutes. 10 g of lauryl sulfonate (in powder form or as a solid) are added and the materials are stirred for 2 minutes.

At this time, 5 g of isooctyl alcohol was added and stirring continued for 4 minutes. 900 g of EKF 120 (125-150 µm) electro-corundum were then weighed into the mixer and the materials were stirred for 10 minutes. Pour distilled water into the mixer (about 100 mL) to adjust the viscosity of the paste to 0.3 Pa.s and continue stirring for an additional 3 minutes. The mixture was then added with a 10% alcoholic solution of 3% cetylpyridinium bromide in alcohol and the mixture was stirred for 5 minutes. The abrasive composition thus obtained (about 1000 ml) is used for grinding carbides.

For carbide grinding, a surface pressure of 0.15 MPa is applied and 0.5 mm is needed to remove 1 mm ^{3 of} material.

The abrasive composition used is regenerated as described in Example 1.

Example 3

The abrasive composition was prepared as described in Example 2, but using a 4159 µm electro-corundum instead of 125-150 µm. The resulting abrasive composition was used for grinding carbide inserts. Thus, the grinding speed was reduced, but curving of the cutting edge of the carbide inserts was avoided. Larger-sized corundum particles are rapidly crushed due to the required higher surface pressure, which causes the original-sized beads to grind faster at the leading edge of the insert than the crushed particles after a distance of two mm. The finishing to the perfect plane can be accomplished by using slightly smaller grains, as this will greatly reduce the compression force acting on each particle, thereby slowing down the grinding process, but also reducing the grinding speed.

For the coating (grinding) of carbide inserts, a surface pressure of 0.2 MPa was applied, and the time required for the removal of ¹ mm ³ was 0.8 sec.

Regeneration of the abrasive composition is a

This was carried out as described in Example 1.

Claims (6)

PATENT CLAIMS CLAIMS 1. A regenerable abrasive sanding composition containing corundum, preferably hard magnets and carbides, characterized in that 50-70 wt. - 2 Pa viscosity, polyacrylic acid sodium having a solids content of 10-15% by weight, 100-500,000 molar, with a surface charge stabilizer of 0.8-1.5% by weight 10-18 20 fatty alcohol sulfonates and 0.3 to 1.0% by weight, preferably 1% by weight, A mixture of C 6 -C 10 aliphatic alcohol and optionally 2.5 to 3.5% by weight, preferably 3 to ² % by weight, of a 10% by weight alcoholic solution of cetylpyridinium halide and 0.3% by weight as a corrosion inhibitor. Contains distilled or deionized water to adjust the viscosity to 1.5 Pa.s. Composition according to claim 1, characterized in that it contains an electro-corundum having a particle size of 150-175 µm. Composition according to claim 1, characterized in that it contains an electro-corundum having a particle size of 125-150 µm. Composition according to claim 1, characterized in that it comprises an electro-corundum having a particle size of 41-59 µm. 5. The composition of claim 1, wherein the aliphatic alcohol comprises hexanes. 6. The composition of claim 1, wherein the aliphatic alcohol comprises isooctyl alcohol. 7. The composition of claim 1 wherein the corrosion inhibitor is 3% by weight of a 10% alcoholic solution of cetylpyridinium bromide.